Congressional Party Defection in American History

Abstract

In this paper, we analyze the roll call voting behavior of those House and Senate members who changed their party affiliation during the course of their political career. We analyze members who switched during the stable periods of the three major twoparty systems in American history: the Federalist-Jeffersonian Republican system (3rd to 12th Congresses), the Democratic-Whig System (20th to 30th Congresses), and the Democratic-Republican System (46th to 106th Congresses). Our primary finding is that the biggest changes in the roll call voting behavior of party defectors is observed during periods of high ideological polarization, and that party defections of the past 30 years are distinct from switches in other eras due both to high polarization and the disappearance of a second dimension of ideological conflict.